Well reaming device



Jan. 3, 1933. A. E. CARLSON WELL REAMING DEVICE 2 Sheets-Sheet l Filed Dec. 15. 1930 Patented .lautI 3, 1933 OFFICE ANTEQNYE. CARLSON, or Los ANGELES, CALIFORNIA* WELL REAMING DEvIcE Application led December 15, 1980. Serial No. 502,353.

My invention relates to rotary well drilling tools and relates particularly to a reaming tool adapted to enlarge the bore of a well. For simplicity in disclosing the essentials of my invention, I am confining this eXposition thereof to a simple embodiment of my invention consisting of an underreamer for use in underreaming a well below the lower end of the casing so that such casing may be 19 readily lowered within the well.. The invention includes cutter elements and simple and efectivemeans for expanding and contracting the cutter elementsy whereby to enable the tool to be lowered into the well in contracted condition, operated therein in eX- panded condition, and then again contracted.

so as to be readily removed through the casing set in\the well above the zone at which the drilling has been conducted. The in- 20 vention lends itself to simplicity and sturdiness in Ya mechanism for controlling the expan'sion and contraction of the cutter elements and maybe embodiedin several types of tools including underreamers and drill- 2"ing tools. l' g It is' an object of the invention to provide a tool of this character having imeans which operate in responseto forward rotation of the drill pipe to move the cutter elements into operating position.

A further object of the invention is to provide a device ofthis character so constructed that inward forc'e exerted against the cutter elements when'the tool is not rotating will operate to move the cutters into retracted position. The invention also'provides means adapted to move the Cutter elements into retracted position in response to engagement of the upper portion of the 40 tool structure.`

A further vobject of the invention is to provide anK underreamer having= cutter rollers adapted to swing from substantially parallel retracted position to outwardly sloping ex- '-j tended position, and means at the upper ends of these rollers for controlling the inward and outward swingmg movement in response to rotation andnon-rotation of the drilling strin C3" A furtherobject of the invention is to proother obstructionin the well formin .striction of the opening through which the fthe followers exerts forces tending to rotate ,the cam in reverse-direction and to rotate the supporting frame of the followers in forward direction.

The invention also provldes one or more' members having downwardly and outwardly sloping spiral engagement edges or ribs which will produce forward rotation of the supporting structure carrying the cam fol- Y lowers when these engagement edges engage the lower end .of a casing set 1n a well, or

a rereamer must pass in being withdrawn from the well. Further objectsand advantages of the 1nvention will be made evident throughout the following part of the specification.

Referring` to the drawings, which are for illustrative purposes only,

Fig. 1 is a partly sectioned elevational view showing a preferred embodiment of my invenion adapted for use in underreaming a wel Fig. 2 is a cross section on a plane represented by theiline 2-2 of Fig. 1.

Fig. 3 is a cross section on a plane represented by the line 3 3 of Fig. 1.

Y Fig. 4 is a -cross section on a plane repre- '90 sented by the line 1e-4p of Fig. 1.

v Fig. 5 is a cross section on a plane represented lby the line 5-5 of Fig. 1.

Fig. 6 is a cross section on a pla-ne represented by the line 6-6 of Fig. 1.

Fig. 7 is an enlarged perspective view of the upper end of one of the roller supporting members for showing my simple form of means for producing forward rotation of the Cutter supporting frame or housing when the tool engages the lower end `of a casing set in a Well. v l

Fig. 8 is a sectional view similar to Fig. 2 showing a simple adjustment means forming part of my invention for controlling the distance the cutters may be swung outwardly.

Fig. 9 is a sectional view-similar to Fig. 8

showing` the manner in which the adjustment diameter than the opening through the casing. Where the drilling is conducted through relatively hard formations, it is necessary to enlarge this lower portion of the hole either .by underreaming or by line reaming. The

simple form of my invention embodied in an underreamer 14 is shown in Fig. 1 in expanded condition so as to underream the hole,

r, in other words, to increase the hole 13 toV such diameter that 'the casing 12,l may be moved downwardly therein. The underreamer 414 includes a stem or body 15 having a threaded pin' 16- at its upper endV for attachment to the lower end of a drilling string,

y such as a string of drill pipe, and having a cylindrical frame structure o'r cutter support 17 mounted on its lower end in a manner to be partly rotatable relative `to the body 15. The cylindrical supportingstructure 17 comprises a cylindrical wall 18,' a lower conical wall 20, andparallel bars 21 extending from the upper wall 18 to the lower wall 20. The

- supporting structure 17 may be looked upon' as a cylindrical member having an upper cylindrical bore 22, a central opening 23, and a discharge opening 24, with radial openings 25 communicating between the exterior of the member` 17 and the central opening 23. The stem or body 15 has a stop lug or boss 26 formed thereon in an intermediate position and below this boss has a cylindrical pin 27 which extends downwardly into the bore 22 of the supporting structure 17. To rotatably secure the stem 15 and the structure 17 together, upper and lower ball recesses I30 and 31 are formed by cutting grooves of semicircular cross section 1n the outer face ofthe' pin 27 and the wall of the bore 22, these re cesses receiving balls 33 through radial openings 34, as indicated in Fig. 3, such openings being closed by suitable-plugs 35 after the balls 33 are placed in the recesses 30 and 31. Extending upwardly from the cylindrical wall is a cylindrically curved stop wall36 of the same thickness as vthe wall 18and having front and rear ends 37 and 38, the angular measurement of the curved or circular length of the wall 36 being approximately 210 so that exteriorly between the ends 37 and 38 of 4the wall is an angular space 40 of substantially 150. The body 26 formed on the stem 15 has a front end 41 and a rear end 42, the angular dimension between the front and rear ends 41 and 42 being substantially 90, thus leaving an angle of movement a between the rear end 42 of the body 26 and the rear end 38 of the wall 36, this angle a determining the relative rotation between the parts 14 and 15.

The walls 45 at the lower ends of the openings 25 in the cylindrical supportingl structure 17 each have a recess or socket 46 4therein, these recesses or socketsv being `disposed on upwardly and outwardly sloping Center lines I), and each socket46 being adapted to receive the semi-spherical or rounded lower end 47 ofva swingable cutter support 48. In the form of the invention illustrated, I provide three radial openings 25, and to correspond therewith there are three cutter supports 48, each of which receives a cylindrical toothed roller-type reaming cutter 50. Each cutter support 48 includes a shaft .portion 52 and a head 53 integrally formed at the upper end of the shaft portion 52. The heads are prisnloidal in form and are received in radial guide openings 54 formed in the frame 17 at the upper ends of the openings 25. The heads 53 have parallel sideffaces 55, as indicated in Fig. 4, which engage the parallel side walls 56 of the guide openings or guides 54. The inward or rearward face of each head 1s cylindrically curved on an axis parallel to the axis of the shaft portion 52 so as to provide the rearward portion of each head 53 with a follower 57 adapted for cooperative engagement with a radial cam face 58 of an actuating cam 59 formed at the lower extremity of the stem 15. Extending upward- Vly from the rearwardportion of the upper face 61 of each head 53 is a stop lug 62 adapted to engage the wall 63 above the cooperating guide opening 54 so as to limit the outward movement of the head 53 1n its guide opening 54. As shown in Figs. 1, 4, 5, and 7, but best shown in Fig. 7, each head 53 has an engagement edge 65 which slopes downwardly, outwardly, and spirally, the spiral direction of the engagement edge 65 being as indicated by the arrow 66 of Fig. 7 'and reverse to the forward rotation of the reamer 14. The purpose of this engagement edge 65, which slopes downwardly and outwardly relative to the axis of the underreamer 14 as shown in Fig. 1, is to cause forward or rightward rotation of the frame 17 when the reamer 14 is moved, with the cutters expanded, upwardly in the well a suiiicient distance to bring the engagement edges into contact with the end 67 of the casing 12. When `-an engagement edge 65 engages the j lower endof the casing 12, the upward force as indicated by an arrow 71 in Fig. 5, which will result in the rearend 38 of the wall 36 shown in Fig. 2 moving toward the' rear end 42tof thebody or lug`26 and likewise will result in movement of the heads 53 rightwardly from the positions in which they are shown in Fig. 5 near the outer ends of the cam faces 58 toward the inner ends 72 of the cam faces so that the inward pressure exerted due to engagement of the engagement faces 65 with the lower end 67 of the casing 12 may move the heads inwardly and swing the cutter supports 48 and cutters 50 from expanded position shown in Fig. 1,-to re-` tracted position shown in Fig. 4. The relative positions of the stop lug 26 and the stop wall 36 shown in Fig. 2 corresponds tothe position of the cam 59 shown in Fig. 5. It will be noted that the cam is stopped in such position that. the followers- 57 of the heads 53 rest against the inwardly sloping outer ends of the cam faces 58, with the result that any inward force exerted against a head 53 tendsy to cause the follower 57 to move rightwardly and inwardlyon its cam face 58, thereby assisting in producing rightward rotation of the 'frame 17 when the outer portions of the heads 53 and the engagement edges 65 come into contact with the lower end 67 of .the casing 12 or other obstruction while the drilling string and reamer are being raised within the well. When the rearward ends 38 and 42 of the wall 36 and the stop lug 26-are in engagement, the cam 59 is in the relative position shown in Fig. 4, with the lower orjinner endsof the cam faces 58 in conjunction with the followers 57,V thereby permitting the cutter supports 48 and the' cutters 50 to rest in retracted position or to swing into retracted position when an inward force is exerted thereon.

The stem 15 is provided with an axial opening adapted to conduct drilling fluid,

such as rotary mud, downwardly from the drilling string. A replaceable orifice or nozzle member 76 is screwed into the lower end of the stern so as to direct the discharge How of drilling fluid into the central opening or space 23 of the underreamer 14. This drilling fluid washes the teeth of the cutters 50, a portion of the drilling fluid passes outwardly through the openings 25 around the cutters 50, an a portion passes downwardly through the opening 24 at the lower end of the underreamer 14 so as to wash ahead of the underreamer during downward pro ress in the hole 13.

T e cutter supports 48 with the cutters 50 mounted thereon may be installed in the openings 25 when the pin 27 of the stern'15 is removed from the bore 22 by entering them through the bore 22 or they may be moved into the central opening 23 head first so that the head 53 will project upwardly into the its bore 22 while the ball ends 47 are inserted in the sockets 46. After the pin 27 has'been locked in the bore 22 by means of the balls 33, the cam 59 limits the inward movement of the heads 53 and prevents removal of the cutter supports and cutters.

By shortening the rotation of the cam 59 relative to the frame 17 yI .am able to control the distance which the cam will force the head 53 outwardly. In Figs. '8 and 9 I show a tangential threaded opening 7() in the stop lug 26 and an adjusting screw 71 of hardened steel threaded therein. The outer end of this A adjusting screw 71 is provided wth a wrench socket 72, and a locking screw 73 is screwed tightly against the outer end to prevent movement of the screw 71 in the threaded opening 70. This locking screwr 7 3 is aalso provided with a wrench socket 74. By moving the screw 71 forwardly so as to project from the threaded opening 70, as indicated in Fig. 9, the effective angular dimension of the stop lug 26 will be increased, therebyklimiting thel l rotation of the stem 15 and the cam 59,rela

tive to the .frame 17, and thereby decreasing the throw of the cam and likewise decreas'ng the dia-meter of the-hole whichthe cutters 50 will ream. As shown in Figs..l0.and 11,

this adjusting means maybe in the form of' an insert block 82 adapted to fit between the ends 37 and 41 of the wall 36 and the lug 26. When'aninsert block 82 is employed, I use a cylindrical wall 83 which extends downwardly from a circular wall or flange 77 at the upper end of the stop lug 26, this cylindrical wall 83 being threaded to the wall or flange 77 at 78 and covering the stop lug 26 and the wall 36 which projects upwardly from the j frame 17. This wall 83 likewise encoses the space 40 and also the space between the ends 37 and 41 of the wall 36 and the stop lug 26, thereby effectively preventing removal of the block 82 whenthe parts-of the reaming device are assembled. The block 82 is held in upright position adjacent the face 41 of the stop lug 26 by means of .a pin 80 which extends downwardlv. into an opening 81 in the upper end of the frame 17 in the manner clearly shown in Fig. v11.

I have specifically described my invention in the form of an underreamer, but the mechanism thereof may be employed in a line reamer so as to operate in conjunction with and above the drilling tcii employed' at the lower end of a string of drill pipe. Although I have herein shown my invention in simple and practica-l form, it is recognized that certain parts or elements thereof are representative of other parts, elements, or mechanisms which may be employed in substantially the same manner to accomplish substantially the same results; therefore, the invention is not to be limited to the details disclosed herein but is to be accorded the full scope of the -following claims.

I claimas my invention:

1. A well reaming tool of the character described, including: a body adapted to'be secured to a drilling' string; cutter members having their lower end supported in said body and their upper ends outwardly swingable, for enlarging the wall of the well; and a spiral cam rotatably mounted in said body for forcing the upper ends of said cutter members outwardly into operative position, said spiral cam being actuated to move said cutter members outwardly in response to relative forward rotation of the drill'ng string, there being means for stopping the rotation of said cam in a position relative to said body in whch sloping faces of said cam are in cngagement with said cutter members so that inward pressure of said cutter members Will tend to rotate said cam in reverse direction.

2. A well reamingtool of the character described, including: abody adapted to be secured to a drilling string; cutter members having theirl lower ends supported in said body and their upper ends outwardly swingable, for enlarging the wall of the well; and a spiral cam rotatably mounted in said body an operating in response toforward rotation of the drilling string for forcing the upper ends of said cutter members outwardly into operative position.

3. A well reaming tool of the character ldescribed, including: a cylindrical body secured to a drilling string, said body having limited rotation relative to the lower end of said drilling string and having` a central opening and radial openings communicating between said central o ening and the exterior of said cylindrical ody; cutter members mounted in said radial openings so as to be outwardly movable therein; a cam in said central opening adapted to be 'rotated by said drilling string so as to move said cutter members outwardly; and adjustable means for limiting the rotation of said cam relative to said cylindrical body.

4. A well reaming tool of the character detheir upper ends outwardly swingable so as to be swunginto diagonal positions relative to the axis of said body; cutters rotatably mounted on saidcutter shafts; and a rotatable memberon the lower end of said drilling string and within the upper portion of said central opening and having cam faces of spiral character for forcing the upper ends ofvsaid cutter shafts outwardly when said drilling string is rotated in forward direction and rotation of said body is resisted.

5. Awell reaming tool of the character described, including: a cylindrical body secured to a drilling string, said body having limited rotation relative to the loweriend of said drilling string and having a central opening and'radial openings communicating between said central opening' and the exterior of said cylindrical body;'cutter shafts supported in said radial openings with their upper ends outwardly swingable; cutters rotatably mounted on said cutter shafts; a cam on the'lower end of said drilling string and within the upper portion of said central opening for forcing the upper ends of said cutter shafts outwardly when said drilling string is rotated-in forward direction; and engagement edges on the upper ends of said cutter shafts sloping downwardly and outwardly and spirally rearwardly so as to produce forward rotation of said cylindrical body in response to engagement with the lower e'nd of a casing set inthe well. v

6. A well reaming tool of the character described, including: a cylindrical body secured to a drilling string, said body having limited rotation relative to the lower end of said drilling string and having a central opening and radial openings communicating between said movable therein; a cam in the upper'portion of said central opening adapted to be rotated by said drilling string so as to move saidcutter members outwardly; means operative in response to engagement-with the lower end of a casing set in the well for producing forward rotation of saidcylindrical body relative to the lower end ofsaid drilling. string; and adjustable means for limiting the rotation of said `cam relative to said lcylindrical body whereby to determine the distance said cutter members will be swung outwardly by said cam.

7. A well reaming tool of the character described, including: a cylindrical body secured scribed, including: a cylindrical body secured to a drilling string, saidl body having a cen- -said central 'opening and the exterior of said cylindrical body; cutter shafts -supported in tral opening and radial openings communieating between said central opening and the exterior of said cylindrical body; Walls forming sockets at the'lower ends of said radial openings; Walls forming radial guides at the upper ends of said radial openings; cutter A 5 said radial openingsin upright positions with supports adapted to be mounted in said ra- 25, cutter supports each comprising a shaft porassenza.:

dial openings, said cutter-supports each comprising a shaft portion, a head on the upper 'end of said shaft portion adapted to move in one of said radial guides, and a socket engaging portion at the lower end of saidshaft portion adapted to rest in asocket in a mannery to permit the head thereofto swing outwardly in said guide; means operative in re` sponse to forward rotation of said drilling string adapted to force said heads of said cutter supports outwardly; and cutters on said cutter supports.

8. A well reaming tool of the character described, including: a cylindrical body secured to 'a drillin string, said body having limited rotation re ative to the lower end 'of said drilling string and having a central opening and radial openings communicating between said central opening and the exterior of said cylindrical body; walls forming sockets at the lower ends of said radial openings; walls formin 'radial guides at the upper ends of said ra ial openings; cutter supports adapted to be mounted in said radial openings, said tion, a head on the upper end of said shaft portion adapted to move m one of said radial ides, and a socket engaging portion at the` ower end of said shaft' portion adapted to rest in a socket in a manner `.to permit the head cam means onthe lower end of said drilling string adapted to force saidvheadsA of said cutter supports outwardly when-said drilling string is -rotated forwardly; and cutters on said cutter supports.

9.' A well reaming tool scribed, including: a cylindrical body secured to a drilling string, said body having a central opening and radial openings communi- .eating between said central yopening and the exterior of said cylindrical body;,walls forming sockets at )the lower ends of saidvradial openings; walls forming radial guides at the upper ends of said radial openings; cuttersupports adapted to be mounted in said radial openings, said-cutter supports each comprisin a shaft portion, a head on the upper end o saidshaft portion adapted to move in one of said radial guides, and a socket engaging portion at the lower end of said shaft portion adapted to rest in a socket in a mauner to permit the head thereof-to swing outwardlyinqsaid guide; means operative in response to forward rotation of said drilling string adapted to force said heads of 4said `cutter supports outwardly; cutters on said cutter supports; and engagement edges .on the outer portions of said heads for producing forward and inward reactionswhen said engagement edges contact the lower end of a casing set in the well, said engagement edges sloping downwardly and outwardly and being spiralled rearwardly.

10. A well reaming tool of the'character of xthe character decured to a drilling string, said body having' limited rotation relative to the lower end of said drilling string and having a central opening and radial openings communicating between said central opening and the exterior of said cylindrical body; 4 walls Iforming sockets at the lower ends of .said radial openings; walls forming radial guides at the upper ends of said radial openings; cutter supports adapted to be mounted in said radial openings, said cutter supports'each comprising aoshaft portion, a head on the upper end of said shaft portion adapted to move in one of said radial guides, and a socket engaging portion at the lower end of -said sha-ft ,portion adapted to rest in a socket in a manner to permit the head thereof to swing outwardly in said guide; cam means on the lower end of said drilling string adapted to force said heads ofsaid cuttersupp'orts outwardly when said drilling string is rotated forwardly; cutters on said cutter supports; and engagement edges on the outer portions of said Y heads for producing forward and inward wardly. thereof Ato swing outwardly in said guide;v

11. A well reaming tool of the character described, including: an body adapted to be secured to a string of drill pipe, said-body having ycutters mounted .thereon so as to be outwardlymovable; means operative in response to. forward rotation of said string Yof drill pipe for moving said cutters outwardly, said means comprising a plurality of cams of spiral character adapted to engage said cutters and move same outwardly when said means is rotated forwardly; a stop for limf iting the rotation of said means relative to I said body in such position that said cutters,

when expanded, will .engage sloping parts of said cams whereby Ainward force exerted against said cutters will tend to rotate said means in reverse direction; and retracting means for saidcutters having engagement edges which slope ddwnwardly and outwardly and spiral rearwardly.

12. A well reaming tool of the character described, including: a body adapted to be rotatably secured to a string of drill pipe, said body having cutters mounted thereon so as to be outwardly movable; means operative in response to forward rotation of said string of drill pipe to move said cutters outwardly, said meanscomprising a plurality of cams of spiral character adapted to engage said cutters and move same .outwardly when said means is rotated forwardly; a stop for limiting the rotation of said means'relative to said body in such position that said cutters, when expanded, will engage slo ing parts of against said cutters will tend to rotate said meansin reverse direction; and retracting `means for said cutters having engagement edges which slope downwardly and outwardly and spiral rearwardly so as to. produce forward rotation of said body .relative to said' 14. A well reaming tool of the character' described, including: a member forming, a part\o\f a drilling string; a'body rotata ly mounted on said member; a cutter movably carried by said body; means for moving said cutter outwardly in response to relative rotation of said body and said member; and adjustable means for limiting the outward movement of said cutter.

15. A well reaming tool of the character described, including: a member forming a part of a drilling string; a body rotatably mounted on said member; a cutter member movably carried by said body, said cutter member having its lower end pivotally connected to said body and its upper end swingable through an upright plane; a cam rotated by said member for moving said cutter member; and retracting means comprising a wall forming an outstanding edge sloping downwardly and rearwardly in a position to iengage an obstruction in the well when moved upwardly andas the result of such engagement to force said cutter member inwardly against said cam and forwardly so as to produce forward rotation of said body relative to said member.

16. A well reaming tool of the character described, including: a member formin a part of a drilling string; a body rotataly 'mounted on said member; a cutter movably carried by saidbody; means Vfor moving said cutter outwardly in response to relative ro-V tationy of said body and said member; a lug on saidbody; a lug on said member; and` means operative between said lugs for determining the extent of rotation of said body relative to said member. I

17. A well reaming tool of the character described, including: a member adapted to be secured to a string of drill pipe, said member 'having circumferential grooves therein and an expanding cam on the lower end thereof; an integral cylindrical body having a bore at its upper end adapted to receive the lower end of said member and having radial openings in the wall thereof below said bore;

cutters carried by said body in said opening' and in position to be actuated by said cam; and means engaging said grooves for holding said body on said member. d

18. A well reaming tool of the character described, including: a member adapted to be secured to a string of drill pipe, said momber having circumferential grooves therein and an expanding cam on the lower end thereof; a body-having a bore at its upper end adapted to receive the lower end of said member; cutters carried by said body in position to be actuated by said cam; means engaging said grooves for holding said body on said member; means forming a radial shoulder on said member above said body; and means on said body providing a shoulder adapted to engage said first named shoulder.

19. A well reaming tool of the character described, including: a member adapted to be secured to a string of drill pipe, said member having circumferential grooves therein and an expanding cam on the lower end thereof;-

an integral cylindrical body having a bore at its upper end adapted to receive the lower end of said member and having radial openings in the wall thereof below said bore; cutof said member; a cutter mounted by said body so as to move radially outwardly; and

a cam on said member within said body having a cam face of spiral character adapted to .engage said cutter and move the same outwardly when said member is rotated relative to said body, said cutter engaging a sloping portion of said cam face when held in outward position by said cam whereby an inward force exerted on said cutter will" tend to rotate said cam due to engagement with said sloping part or portion of said cam face.

21. A tool 4of the character described, in-

cluding: a body having an axial opening and having radial `openings communicating with said axial opening for receiving cutters; cuttersin said radial openings adapted to move outwardly, there being stop means cooperating between said body and said cutters for limiting the outward movement of. said cutters.; a member adapted to be secured to a string of drill pipe, said member having an end portion adapted to t into said aXial opening of said body and to project into a position behind said cutters so as to limit the inward movement thereof; means connected to said end portion of said member for actuating said cutters, there being a fluid passage extending into said axial opening; a rotary through said member for discharging iuid into the space of said axial opening behind said cutters; and means for securing said body tosaid member. y

22. A tool of the character described, in? cluding: a body having an axial opening and having radial openings communicating with said axial opening for receiving cutters; cutters in said radial openings adapted to move outwardly; a memberadapted to be secured to a string of drill pipe, said member having an end portion adapted to lit into an end of cam on said mandrel for actuating said cutters; stop means cooperating between said mandrel and said body for limiting the movement thereof; and means for rotatably securing said mandrel to said body.

In testimony whereof, I have hereunto set my hand -at Los Angeles, California, this 9th day of December, 1930.

ANTHONY E. CARLSON.

said axial opening of said body so as to leave an open space in said axial openingbehind said cutters; means connected to said end portionv of said member for actuating said cutters, there being acfluid passage through said member for discharging fluidv into theV space of said axial opening behind said cut-4 ters; and means for securing said body to said member.

23. A tool ofthe character described, including: a body having an axial opening and having radial openings communicating with said axial opening for receiving cutters; roller type reaming cutters in said radial openings adapted to move outwardly, there being stop means cooperating between said body and said cutters for limiting the outward movement of said cutters; a member adapted to be secured to a string of drill pipe, said Y member having an end portion adapted to fit into said axial opening of said body and to project into a position behind said cutters so as to limit the inward movement thereof;

means connected to said end portion of said ,member for actuating said cutters, there being a Huid passage through said member for discharging fluid into the space of said axial opening behind said cutters; and means for securing said body to said member.

24. A tool of the character described, including: abody comprising a cylindrical wall having an axial opening and having radial openings communicating with said axial opening for receiving cutters; cutters in said radial openings adapted to move outwardly; a member adapted to be secured to a. string of drill pipe, said member having an end portion adapted to` t into an end of said axial. opening of said body so as to leave an open space in said axial opening behind vsaid cutters; means connected to s'aid end portion of said member for actuating said cutters, there being a iiuid passage through said member for discharging fluid into the space of said axial openingbehind said cutters; and means for securing said body to said member. 50 25. A tool of the character described, in-

- cluding: a cylindrical body having an axial opening and radial openings communicating with said axal opening; cutters mounted in i said radial o enings so as to be moved outwardlytherein; a mandrel having -a portion 

